Mander grew up on the northern New Zealand frontier and had little formal schooling. At the age of 15 she taught primary school while completing her high-school education under a tutor. When her father purchased a newspaper, the Northern Advocate, Mander worked there as a reporter from 1902 to 1906. In 1912 she moved to New York City in order to study journalism at Columbia University. While in the United States she became involved in the woman suffrage movement and wrote her first three novels, all set in frontier New Zealand. The independent female protagonists of these novels are, in part, self-portraits.

The Story of a New Zealand River (1920) contrasts the life of a cultivated, educated, lonely woman who maintains strict social and moral values in a frontier settlement with that of her uninhibited daughter, who finds employment in Australia and lives with her lover. It was one of the first significant novels to come out of New Zealand. Mander’s other novels include The Passionate Puritan (1921), the story of a lively young frontier schoolteacher who is attracted to an irresponsible married man, and The Strange Attraction (1922), in which another young woman seeks financial and romantic independence while living on the frontier. In 1923 Mander moved to London, where she wrote three more novels, Allen Adair (1925), The Besieging City (1926), and Pins and Pinnacles (1928). After she returned to New Zealand in 1932, she limited her writing to journalism.